Insecticide poisoning has claimed several lives in the past couple of months, with at least 21 farmers dying in Yavatmal alone. While several explanations have been put forth for the deaths, one common factor among these cases has been the use of harmful pesticides. One such pesticide is monocrotophos.
Monocrotophos, which has been found to be in common usage in Yavatmal among other substances, has been in the news before. The internationally banned pesticide, which is known to make plants look green and healthy, was linked to the death of 23 school children in Bihar in 2013.
C Jayakumar, director of the Pesticide Action Network, says monocrotophos is one of the oldest pesticides still in use, and although it is known to be toxic, it is not alone.
"There are two kinds of toxic pesticides: acute ones which cause immediate effect, and chronic pesticides which have a built-up effect over a long period of time," Jayakumar explained. "Now governments usually move away from most of these acutely toxic ones because it creates immediate and visible problems. Monocrotophos is an highly acutely toxic. But somehow, it is still used for non-food products."
The World Health Organisation has placed monocrotophos in Class 1b — a category reserved for highly hazardous pesticides. "The substance was banned in 2005 in India for use on vegetables. Currently, monocrotophos is mostly used to grow cotton," Dileep Kumar, programme coordinator in Pesticide Action Network, said.
"If you decide to ban 10 percent of the most lethal pesticides in the country at the moment, monocrotophos will be one of them," Jayakumar said.
Multiple routes of exposure
Monocrotophos can be absorbed into the human body through multiple pathways, including inhalation, skin contact and ingestion, and is acutely toxic by all routes of exposure. The first two modes of exposure put Indian farmers at an unusually high risk.
"Farmers here mostly work without any protective equipment, and this puts them at risk of pesticide uptake by inhalation and absorption through the skin," Kumar said.
How monocrotophos affects the body
Monocrotophos is an organophosphate insecticide, which is a type of pesticide. These kinds of pesticides are known to be neurotoxins, which affect the work of neurons in the body. Monocrotophos is found to be lethal because of its action on the central nervous system of the human body. Here is a broad breakdown of the process with generous inputs from Kumar:
The nervous system is made up of a large and complex network of nerves. When a signal reaches the end of a nerve, it releases a substance called neurotransmitter that carries the signal to the adjacent nerves or organ. Many nerves in the nervous system release a neurotransmitter called acetylcholine. Once the signal passes onto the next nerve, an enzyme called acetylcholinesterase destroys the acetylcholine. And this is where monocrotophos comes in.
Organophosphorus compounds, like the pesticide at hand, block this enzyme, thus preventing the breakdown of acetylcholine. And hence, acetylcholine acts for an excessively long period of time, causing symptoms like twitches and increased secretions at the junctions between nerves. After a long duration of this process, muscles get fatigued leading to paralysis.
This also prevents communication in the nervous system, either between two nervous cells or between a nervous cell and a muscle cell. If this spreads throughout the body, death of the affected person becomes a highly likely outcome.
Monocrotophos, like other organophosphate insecticides, is highly toxic by all routes of exposure. Here are the symptoms, again with inputs from Kumar:
When inhaled, the first effects are usually respiratory. They may include a bloody or a runny nose, coughing, chest pain, short breaths and wheezing due to constriction or excess fluid in the bronchial tubes.
Skin contact with this pesticide may cause localised sweating and involuntary muscle contractions.
Eye contact will cause pain, bleeding, tears, pupil constriction and blurred vision.
Following exposure by any route, other systemic effects will either begin within a few minutes or may show up after up to 12 hours. These may include pallor, nausea, vomiting, diarrhoea, abdominal cramps, headache, dizziness, eye pain, blurred vision, constriction or dilation of the pupils, tears, salivation, and sweating.
Severe poisoning will affect the central nervous system, producing incoordination, slurred speech, loss of reflexes, weakness, fatigue, involuntary muscle contractions, twitching, tremors of the tongue or eyelids, and eventually paralysis of the body extremities and the respiratory muscles.
In severe cases, there may also be involuntary defecation or urination, psychosis, irregular heartbeat, unconsciousness, convulsions, and coma. Respiratory failure or cardiac arrest may even cause death.
"I hope the government sees through the obvious health implications of this pesticide soon and take into account the toll it has already taken on farmers and other citizens," Jayakumar added.
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Updated Date: Oct 17, 2017 16:01:52 IST